The selective catalytic reduction (SCR) of nitric oxide (NO) by ammonia (NH3) at 393-473 K over AC (activated carbon) supported V2O5 (vanadium pentoxide) (V2O5/AC) catalyst in the presence of H2O was investigated. In order to understand the influence of H2O on reaction rate and reaction mechanism, the kinetic measurement was performed. Both mechanistic and empirical models were applied to correlate the experimental data. The results showed that the SCR reaction follows the Eley-Rideal mechanism rather than Langmuir-Hinshelwood or Mars-van Krevelen mechanisms whether H2O was contained or not. And the pre-exponential factor decreased and activation energy increased with the increasing amount of H2O. But at high H2O content, the kinetic parameters were almost unchanged with the further increase of H2O content. Finally, the intrinsic kinetic models obtained in this work were incorporated into a 3D mathematical model of monolithic reactor. It was found that the Eley-Rideal model was more suitable for describing the SCR of NO by NH3 in the presence of H2O than the empirical models, and thus should be adopted in the actual reactor design and scale-up for controlling the emission of NOx. (C) 2012 Elsevier B.V. All rights reserved.